An electroluminescent (EL) display is one of the most remarkable devices as a flat panel display device for the next generation, which is composed of a light emitting element. In a light emitting element, electrons injected from a cathode and holes injected from an anode are recombined in a light emitting layer when current is flowed to form molecule excitons. The light emitting element emits light by using photons discharged when the molecular excitons return to the ground state. Therefore, one of conditions to manufacture a light emitting element having favorable emission efficiency is to use whole excitation energy of molecule excitons for light emission.
One example which meets the above condition is a multilayer structure of a light emitting element. For example, a multilayer is formed of a hole injecting layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injecting layer, and the like between a pair of electrodes including an anode and a cathode.
Further, the effective injection of holes and electrons, which are carriers, to a light emitting layer is also one of the conditions to manufacture a light emitting element having favorable emission efficiency. For that purpose, it is conventional and known that a material having low ionization potential is used for a hole injecting layer and a material having high electron affinity is used for an electron injecting layer.
Such a layer included in a multilayer structure of a light emitting element described above is formed from metal oxide which is an inorganic compound, or an organic compound.
In addition, an attempt to form a light emitting element using a layer in which an organic compound is mixed with an inorganic compound has been made. For example, a light emitting element formed by stacking a layer formed from a material dispersed with an organic compound (a hole transporting compound, an electron transporting compound, and a luminescent compound) in a silica matrix via a covalent bond is disclosed in the following Patent Document 1 (Patent Document 1: Japanese Patent Application Laid-Open No. 2000-306669). In the Patent Document 1, it is reported that durability or heat-resistance of an element is enhanced.